Earth and Planetary Science Letters最新文献

{"title":"Garnet clinopyroxenite formation via amphibole-dehydration in continental arcs: Evidence from Fe isotopes","authors":"Emma S. Sosa ,&nbsp;Claire E. Bucholz ,&nbsp;Juan David Hernández-Montenegro ,&nbsp;Andrés Rodríguez-Vargas ,&nbsp;Michael A. Kipp ,&nbsp;François L.H. Tissot","doi":"10.1016/j.epsl.2024.119050","DOIUrl":"10.1016/j.epsl.2024.119050","url":null,"abstract":"<div><div>Lower-crustal garnet clinopyroxenite (sometimes termed “arclogite”) fractionation in thick-crustal (&gt;35 km) arc settings presents a compelling model to explain Fe-depletion trends, high oxygen fugacity, and evidence of recent delamination observed in many continental arcs. However, the origin of the garnet clinopyroxenites via igneous or metamorphic processes remains unclear. Due to the preferential incorporation of light Fe isotopes in garnet relative to clinopyroxene or amphibole, Fe isotopes are ideally suited for studying the effects of garnet fractionation on magmatic systems. Here, we present whole-rock and mineral Fe isotope data from a suite of lower to mid/upper-crustal Andean xenoliths from Mercaderes, Colombia. This data is combined with petrography, major and trace element mineral and whole-rock chemistry, geothermobarometry, and thermodynamic modeling to explore the xenoliths' petrogenesis and the Northern Andes' crustal structure. Whole-rock samples display a narrow range of Fe isotope compositions (δ⁵⁶Fe = –0.02 to +0.11 ‰), which do not correlate with lithology, chemistry, or pressure-temperature conditions. This result is inconsistent with previous studies predicting the existence of an isotopically light Fe reservoir in the garnet-rich lower Andean crust. Through thermodynamic modeling, we show that the lack of isotopic fractionation in the Mercaderes xenoliths is more consistent with the suite representing a prograde metamorphic sequence, in which amphibole dehydration reactions drive metamorphism of mid/upper-crustal diorite protoliths. While our data do not preclude the presence of garnet clinopyroxenite cumulates at the base of the Andean crust, or that the delamination of such cumulates played an important role in the evolution of the Andes, they do indicate that not all garnet clinopyroxenites are cumulate in origin. Instead, the lower Andean crust represents an amalgamation of igneous and metamorphic rock, with metamorphism of mid-crustal lithologies and partial melting of mafic cumulate roots acting in tandem to drive densification and delamination of the lower crust in a self-feeding mechanism.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"648 ","pages":"Article 119050"},"PeriodicalIF":4.8,"publicationDate":"2024-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142534638","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Earth's hypsometry and what it tells us about global sea level","authors":"V.K. Pedersen ,&nbsp;N. Gomez ,&nbsp;J.X. Mitrovica ,&nbsp;G. Jungdal-Olesen ,&nbsp;J.L. Andersen ,&nbsp;J. Garbe ,&nbsp;A. Aschwanden ,&nbsp;R. Winkelmann","doi":"10.1016/j.epsl.2024.119071","DOIUrl":"10.1016/j.epsl.2024.119071","url":null,"abstract":"<div><div>Over geological time scales, the combination of solid-Earth deformation and climate-dependent surface processes have resulted in a distinct hypsometry (distribution of surface area with elevation) on Earth, with the highest concentration of surface area focused near the present-day sea surface. However, in addition to a single, well-defined maximum at the present-day sea surface, Earth's hypsometry is also characterized by a prominent maximum ∼2–5 m above this level, with the range accounting for uncertainties in recent digital elevation models. Here we explore the nature of this enigmatic maximum and examine, using a gravitationally self-consistent model of ice-age sea-level change, how it evolved over the last glacial cycle and may evolve moving towards a near-ice-free future. We argue that the hypsometric maximum captures topographic conditions at the end of the last deglaciation phase and subsequent glacial isostatic adjustment (GIA) raised it from the sea surface to its present-day elevation. Moreover, ongoing GIA will raise the maximum a further ∼2 m in the absence of future ice mass loss. If a portion of the hypsometric maximum has persisted for longer than Holocene time scales, the resulting GIA-converged elevation of the hypsometric maximum at +4–7 m above the sea surface implies a longer-term mean state of the Earth that may reflect lower ice volumes, trends in erosion, dynamic topography, or a combination of these. The signature of these various contributions on present-day hypsometry is intimately connected to the time scale of erosional and depositional processes near shorelines.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"648 ","pages":"Article 119071"},"PeriodicalIF":4.8,"publicationDate":"2024-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142534121","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Orbital identification of widespread hydrated silica deposits in Gale crater","authors":"Marie Kepp ,&nbsp;Lu Pan ,&nbsp;Jens Frydenvang ,&nbsp;Martin Bizzarro","doi":"10.1016/j.epsl.2024.119082","DOIUrl":"10.1016/j.epsl.2024.119082","url":null,"abstract":"<div><div>The Mars Science Laboratory has been investigating the central mound of Gale crater since 2012 and revealed evidence of silica enrichment in several locations, suggesting that the geologic processes related to the formation of hydrated silica could be widespread. A reanalysis of orbital data over Aeolis Mons indicates the existence of an extensive unit rich in hydrated silica. These silica-enriched deposits, found at the base of Aeolis Mons, span elevations from -4513 m to -3351 m. The mapped hydrated silica deposits are spatially adjacent to an erosion-resistant capping unit, previously mapped as the mound skirting unit, which lies beneath the terminal deposits from local canyons and valleys. We hypothesize that the hydrated silica-bearing unit precipitated from groundwater which migrated upwards or deposited as a volcaniclastic silica-rich layer which was rehydrated during the late-stage canyon and valley forming events. The silica-bearing unit beneath the capping unit is protected against erosion by younger fan-shaped deposits and became exposed only recently. The mineralogy and stratigraphic relations with Mount Sharp units imply that the aqueous activities leading to silica diagenesis were likely a basin-wide process that occurred long after the formation of lakes in Gale crater's geological history and experienced limited water-rock interaction since then.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"648 ","pages":"Article 119082"},"PeriodicalIF":4.8,"publicationDate":"2024-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142534637","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Low total REE zircon formed in equilibrium with hornblende in granulitized eclogites: Implications for exhumation rates","authors":"Jia-Min Wang ,&nbsp;Daniela Rubatto ,&nbsp;Pierre Lanari ,&nbsp;Yu-Lu Tian ,&nbsp;Yi Chen ,&nbsp;Fu-Yuan Wu","doi":"10.1016/j.epsl.2024.119084","DOIUrl":"10.1016/j.epsl.2024.119084","url":null,"abstract":"<div><div>Exhumation rates of high-pressure rocks are paramount in determining plate tectonic processes, which requires absolute chronology of metamorphic stages. U-Pb geochronology of zircon and other accessory minerals has proven successful in dating different metamorphic stages, thus constraining geological rates. A common strategy to link U-Pb ages to metamorphic stages uses rare earth element (REE) patterns in the dated minerals. In this study, the changes in the REE composition of accessory and rock-forming minerals in response to changing assemblages have been investigated in granulitized eclogites and gneisses from the Ama Drime Massif, central Himalaya. Phase equilibrium modelling shows that the eclogite-facies assemblage formed at 660–720 °C and 1.6–1.9 GPa (M1), was overprinted at high-pressure granulite-facies (M2) and then ultra-high temperature conditions of &gt;900 °C and 0.8–1.1 GPa (M3) and finally re-equilibrated at conditions of 780–810 °C and 0.8–1.0 GPa (M4). In the countryrock orthogneisses, monazite records partial resetting during granulite-facies overprinting at 26–19 Ma and melt crystallisation at 16–13 Ma, supported by textures, mineral inclusions and trace elements. In the associated granulitized eclogites, zircon records only granulite/amphibolite facies overprinting at ∼14 Ma, and titanite and rutile record cooling to 580–630 °C at 12.5–9 Ma. Granulite/amphibolite facies zircon has a low total REE relative to the protolith zircon, primarily due to the growth of REE-rich hornblende (total REE 80–260 μg/g), which removed 67–92% of the REE from the system. The low total REE of granulite/amphibolite facies zircon is comparable to the flat HREE reported for garnet-rich eclogite-facies zircon, and distinguishing these zircon types requires quantitative mineral volume estimates and other criteria. These findings may imply slower exhumation rates for some eclogite-facies terranes, such as the Tso Morari Himalaya and Papua New Guinea, than previously reported.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"648 ","pages":"Article 119084"},"PeriodicalIF":4.8,"publicationDate":"2024-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142534636","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Multiple hydrothermal events at martian surface revealed by H and Cl isotope systematics of melt inclusions and hydrous minerals from chassignite NWA 2737","authors":"Sen Hu ,&nbsp;Mahesh Anand ,&nbsp;Ian A. Franchi ,&nbsp;Xuchao Zhao ,&nbsp;Alice Stephant ,&nbsp;Magali Bonifacie ,&nbsp;Huicun He ,&nbsp;Wei Yang ,&nbsp;Jialong Hao ,&nbsp;Yangting Lin","doi":"10.1016/j.epsl.2024.119072","DOIUrl":"10.1016/j.epsl.2024.119072","url":null,"abstract":"<div><div>The chassignites and nakhlites could have co-magmatic origin but display distinct hydrogen and chlorine isotopic compositions, indicating that they may have experienced distinct hydrothermal activities on Mars. However, the details are not yet fully understood. Here, we performed H and Cl isotopic investigations on hydrous minerals (kaersutite and apatite) and glass-bearing melt inclusions from chassignite NWA 2737 to unravel the details of the hydrothermal events experienced by chassignites on Mars. Our results demonstrate that at least two hydrothermal events on Mars have been recorded in NWA 2737. A D- and ³⁷Cl-rich martian crustal/underground fluid was added to the parent magma of NWA 2737 prior to the entrapment of melt inclusions and later interaction of the parent rock with a D-poor fluid, probably deriving from magma degassing. The notable high-δD values (up to 6239‰) of kaersutite in NWA 2737 are comparable with those recorded in younger shergottites, suggesting that the martian exchangeable water reservoir has retained a nearly constant δD value over the past 1.3 Ga.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"648 ","pages":"Article 119072"},"PeriodicalIF":4.8,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142441207","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"2D numerical experiments on a plume-fed asthenosphere: Necessary preconditions and implications for geoid and dynamic topography","authors":"Ya-Nan Shi ,&nbsp;Jason P. Morgan ,&nbsp;Chao Shi","doi":"10.1016/j.epsl.2024.119068","DOIUrl":"10.1016/j.epsl.2024.119068","url":null,"abstract":"<div><div>We explore the conditions necessary for mantle flow to include a plume-fed asthenosphere (PFA) as a key structure within its large-scale flow pattern. Using 2D finite element-based experiments, we examine temperature-dependent rheological effects of ridge accretion, plate cooling, and numerically well-resolved ∼10–30 km-thick asthenosphere dragdown by subducting slabs. We find that an average plume flux ∼1.2 times big as the average slab flux is needed to maintain a persistent PFA. These numerical experiments also demonstrate that, instead of generating dynamic topography on the sea floor, flow-induced dynamic relief due to sub-asthenospheric density anomalies will preferentially form at the buoyancy contrast associated with the base of a buoyant asthenosphere. This mode of dynamic internal relief may contribute significantly to near-surface density anomalies that are associated with Earth's low-order geoid, and local relief at the base of the asthenosphere near plumes, ridges, and trenches that can be imaged in seismic experiments.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"648 ","pages":"Article 119068"},"PeriodicalIF":4.8,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142441206","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Water ice particles detected by SELENE's Spectral Profiler at lunar shadowed regions in various local times and latitudes","authors":"Kosei Toyokawa ,&nbsp;Junichi Haruyama ,&nbsp;Takahiro Iwata ,&nbsp;Hitoshi Nozawa","doi":"10.1016/j.epsl.2024.119065","DOIUrl":"10.1016/j.epsl.2024.119065","url":null,"abstract":"<div><div>Processes of water (OH and H₂O) migration on the Moon remain unclear, prompting active research. Understanding lunar water migration requires investigation of the trapping and diffusion properties of water at various latitudes and local times. This study analyzed visible to near-infrared spectral data obtained by the Spectral Profiler (SP) onboard SELENE for shadowed regions at various local times and latitudes, not limited to the polar permanently shadowed regions. We assessed SP data for shadowed regions in 60 areas, each spanning a 10° × 10° latitude–longitude grid. Of the 1,061,907 analyzed shadowed-region data, 41,385 at various latitudes exhibited significant absorption in the 1.25 and 1.5 µm bands, indicating water ice particles. Data with the two absorption features suggest the presence of a water ice frost layer covering the lunar surface or suspended water ice particles above the lunar surface, at various latitude shadowed regions. Our spectral simulations have quantified the ice particles as being 0.1–1 µm in diameter, with a column density of 10^–4–10^–3 kg/m². The spectral parameters for band absorption at the 1.5 µm band show symmetry between morning and evening sides, which is potentially attributed to the absence of variations in ice grain size and quantity. The 1.5 µm band absorption shows an increasing trend toward terminator regions, indicating variation in the water ice distribution and likely reflecting temperature conditions for water retention. The latitudinal trend of ice grain size and quantity remains uncertain because of the observed noise levels. Observations of water ice particles in shadowed regions at various latitudes and local times can provide new constraints on trapping and diffusion processes of lunar water migration.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"648 ","pages":"Article 119065"},"PeriodicalIF":4.8,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142433930","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Tracing hydrous eclogite melts in the source of sanukitoids","authors":"L.M. Spencer ,&nbsp;C. Albert ,&nbsp;H.M. Williams ,&nbsp;O. Nebel ,&nbsp;I.J. Parkinson ,&nbsp;R.H. Smithies ,&nbsp;H. Bruno ,&nbsp;M. Fowler ,&nbsp;H. Moreira ,&nbsp;C.J. Lissenberg ,&nbsp;M.-A. Millet","doi":"10.1016/j.epsl.2024.119067","DOIUrl":"10.1016/j.epsl.2024.119067","url":null,"abstract":"<div><div>Sanukitoids are unique Archean and early Proterozoic igneous rocks. They contain high amounts of Mg, Ni and Cr, showing they are mantle-derived melts, while they are also enriched in Sr and Ba and have relatively high K contents, requiring the involvement of an incompatible element-enriched component likely derived from recycled crustal material. The appearance of sanukitoids in the geological record coincides with a shift in continental crust composition, and both events have been linked to a change in geodynamic processes on Earth. However, uncertainties remain about sanukitoid petrogenesis, in particular whether their mantle source was metasomatised by a metabasite-derived silicate melt or by an aqueous fluid. Titanium (Ti) stable isotopes can trace magmatic processes where silicate melts are in equilibrium with Fe-Ti oxides and amphibole but are insensitive to fluid-driven processes, making them a suitable tool to investigate not only the formation of sanukitoid magmas but also their subsequent evolution. Here we present Ti isotope data (δ⁴⁹Ti) for a series of Neoarchean sanukitoids from the Yilgarn Craton that continuously covers the full compositional range of sanukitoids. These are complemented by Mesoarchean sanukitoids and Paleoarchean “sanukitoid-like” rocks from the Pilbara Craton, and by Paleoproterozoic sanukitoids from the São Francisco Craton/Paleocontinent. In addition, we analysed Paleozoic high Ba-Sr granite suites from Scotland, which are proposed to be Phanerozoic sanukitoid analogues.</div><div>Evolved sanukitoids, which formed after Fe-Ti oxide saturation, show a more muted δ⁴⁹Ti increase during differentiation compared to currently analysed modern calc-alkaline suites. This difference is best explained by removal of significant proportions of Ti during sanukitoid differentiation by magmatic hornblende, which fractionates Ti isotopes less strongly than Fe-Ti oxides. Combined with early oxide saturation at high Mg#, this suggests that sanukitoid parental magmas had H₂O contents and fO₂ at least as high as modern arc magmas. Primitive (pre-oxide saturation) sanukitoids, however, have significantly higher δ⁴⁹Ti (0.11–0.20‰) than modern arc basalts, the depleted mantle and the bulk silicate Earth (BSE). Their elevated δ⁴⁹Ti values cannot be explained by aqueous fluids alone in their mantle source, and instead require the involvement of a hydrous eclogite melt component formed in equilibrium with residual rutile. We favour generation of this metasomatic melt by fluid-fluxed eclogite partial melting, demonstrating that both metabasite melts and aqueous fluids are important for sanukitoid formation. The Ti isotope compositions of Archean and Paleoproterozoic sanukitoids therefore favour formation of the sanukitoid mantle source by a subduction-like process at least ∼2.7 Ga.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"648 ","pages":"Article 119067"},"PeriodicalIF":4.8,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142441205","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The viscosity of a partially molten layer in a paleo-orogenic plateau","authors":"Z. Molitor ,&nbsp;T. Mittal ,&nbsp;O. Jagoutz","doi":"10.1016/j.epsl.2024.119060","DOIUrl":"10.1016/j.epsl.2024.119060","url":null,"abstract":"<div><div>Orogenic plateaus (e.g., Tibet, Altiplano) are characterized by broad, flat-top topography at high elevation and significantly increased crustal thickness. Partial melt is thought to weaken the middle crust of orogenic plateaus, and thus reduce the viscosity of the crust; however, the amount of partial melt and the magnitude of associated weakening remain unconstrained. The New England Appalachians represent an exposed mid- to lower crustal section of a paleo-orogenic plateau, similar to modern-day Tibet. In this study, we utilize the relationship between the spacing of deformation bands and the compaction length to constrain mid-crustal shear viscosity in a late Devonian migmatite. We find that the viscosity of the middle orogenic crust in the paleo-orogenic plateau of the New England Appalachians is 10^17–18 Pa∙s at ∼3–9% melt. This finding is consistent with geophysical models of orogenic channel flow and provides field-based evidence for a significant rheologic transition at low melt-fraction. Our results suggest that the key elements for the formation of a weak, mid-crustal layer in orogenic plateaus are an influx of water and temperatures near the hydrous granite solidus.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"648 ","pages":"Article 119060"},"PeriodicalIF":4.8,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142441204","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Detection of a ULVZ in the Central Pacific using high frequency Sdiff postcursors","authors":"Carl Martin ,&nbsp;Stuart Russell ,&nbsp;Sanne Cottaar","doi":"10.1016/j.epsl.2024.119028","DOIUrl":"10.1016/j.epsl.2024.119028","url":null,"abstract":"<div><div>In recent decades, ultra-low velocity zones (ULVZs) – thin patches of strongly reduced seismic velocity atop the core-mantle boundary (CMB) – have been inferred from observations of a variety of seismic phases. One such phase is Sdiff and its out-of-plane postcursory energy, Sdiff+. In this study, we present a high quality dataset of Sdiff and Sdiff+ which shows evidence of a ULVZ in the central Pacific, roughly between Hawaii and Marquesas. The observed Sdiff+ have an unusually short dominant period (5–12 seconds) compared to previous Sdiff+ observations, which is indicative of a ULVZ that is approximately 10–15 km thick. We analyse this high frequency dataset using the 2D Wavefront Tracker (2DWT) Bayesian inversion methodology to generate a probabilistic ensemble of ULVZ models. As a result of the uniazimuthal coverage of data, there is a strong southwest-northeast trade-off, but there is a slight preference for the ULVZ to be located just outside the Pacific large low velocity province (LLVP) boundary, roughly centred 20° north of Marquesas and 20° southeast of Hawaii. The 2DWT inversion of Sdiff+ travel times suggest that the ULVZ can be approximated as a cylindrical structure; either as a larger and weaker anomaly (radius 280 km, dVs -20%) close to the LLVP, or a smaller and stronger anomaly (radius 180 km, dVs -30%) further away from the LLVP. Unlike previous broad-scale ULVZs modelled with Sdiff+, this ULVZ is thinner, might lie outside of an LLVP, and lacks a potential relationship to a mantle plume.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"648 ","pages":"Article 119028"},"PeriodicalIF":4.8,"publicationDate":"2024-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142433931","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}